1. Field of the Invention
This invention relates to systems for presenting visual stimuli often referred to as tachistoscopes. More particularly, this invention relates to systems for selectively lateralizing the input of visual stimuli by occluding parts of the visual field and thereby separately stimulating the different hemispheres of the cortex.
2. State of the Art
Recent studies have revealed specializations in the functions of the right and left cerebral hemispheres of the cortex. It has therefore become important to separately study and train the cerebral hemispheres. This may be accomplished by selectively applying visual stimuli to different areas of the occular retinas since the left and right sides of the retinas are coupled to different hemispheres of the cortex. Consequently, by occluding vision from one side of a retina and thereby presenting stimuli in a lateralized form the right and left hemispheres of the visual cortex may be separately (hemianoptically) stimulated.
In the past, study and training through hemianoptical stimulation have been effected by the use of mechanical shutter devices which present information to subjects who would sit with their heads clamped in a stable position watching a central fixation point. However, with this technique, information can only be presented for short periods before naturally occurring eye movements alter the visual field of the subject. Alternatively, contact lenses of special construction have been used to achieve hemianoptic stimulation. These lenses are covered with opaque material except for vertical slits decentered from the optical axis or they are attached to collimator assemblies including caps for occluding the visual field. However, these devices are uncomfortable for many subjects to use and do not allow for simultaneous stimulation of both hemispheres.
The present invention helps to overcome the aforementioned limitations by providing a system for hemianoptical visual stimulation which is effective yet easy to utilize, allows complex and rapidly changing images to be presented, permits extended exposure periods to stimuli, and provides for effectively simultaneous stimulation of both hemispheres with different stimuli.